Pneumothorax, while easily treatable, can become life-threatening if not detected at an early stage. Current devices for diagnosing pneumothorax (chest x-ray, chest CT scan, and stethoscope) are impractical for emergency squads or chaotic trauma care situations. A portable handheld pneumothorax detector that is inexpensive, accurate, and non-invasive would be very attractive commercially. We propose in Phase I to build and test such a prototype device based on micropower impulse radar (MIR) technology. A MlR device fulfills the above technical requirements for trauma care environments and would be ideal as a pneumothorax detector. In Phase I, we will test the device using phantom models and animal models to verify its efficacy. We will also investigate human factors to develop an appropriate design for field use, and we will evaluate the operating characteristics of the device. In Phase II, we will build an optimized handheld device and validate the technique on human subjects. PROPOSED COMMERCIAL APPLICATIONS: A handheld inexpensive pneumothorax detector will be commercially attractive to emergency medical personnel and trauma clinicians. With further development, the device may be tuned to detect other trauma conditions, such as hematoma and hemorrhagic stroke.